The invention relates to a method and a sensor unit for detecting “sugar end” defects in potatoes.
The invention further relates to a machine for treating potatoes having “sugar end” defects.
The detection and subsequent sorting of bulk material using cameras is a rather common method. One embodiment of such a plant for sorting potatoes is, e.g., described in the patent U.S. Pat. No. 4,351,437A. In this known plant, potatoes are conveyed on a roller table conveyor, wherein they are moved arranged in transverse rows to an inspection region, in which they are irradiated by light in an incident light method and the light reflected from the potatoes is captured by a line scan camera. The line scan camera regularly scans transversely across each row of potatoes and generates a detection output signal corresponding to the reflected light. The camera thus views a brightly illuminated region of the potatoes against a dark background so that a microprocessor may determine from the images captured in this way the length of the potatoes in the direction of the row of potatoes.
Further plants for sorting and analyzing foodstuff are described in EP 672 468 B1 or EP 1 332 353 B1. Most common is the incident light detection and sorting of conveyed objects, wherein the conveyed objects are inspected completely automatically, wherein light is projected onto the objects and the reflected light is received by a camera and then analysed. The light is either wide-band or filtered white light, it may also be configured as LED or laser light having particular wavelengths for the relevant task to be performed Impurities at the object surface may be recognized using this technology, but also certain quality differences in the bulk material.
Recently, more and more spectroscopic technologies have been used for analyzing and inline sorting foodstuff. By means of a so-called “flavour” or “taste analyser”, the sugar content of entire fruits is being analysed, for example. An embodiment of such a device is described in the patent U.S. Pat. No. 7,103,207 or configured as a hand-held tool in WO 99/61898 A1. These methods function on the basis of a single-channel spectrometer. Therewith, the reflectance and/or transmission behaviour of a single measurement point or measurement spot of an object is recorded and analysed.
Many defects and impurities of fruits and vegetables, however, cannot be recognized using these known technologies. In particular the so-called “sugar end” defects and potatoes, which are known in the literature as “sugar-ends”, cannot be clearly recognised, as these are local defects of growth in the potato tuber. In these local growth defects, there is developed an accumulation of sugars at the stem end, in particular at the proximal end of the potato tubers, caused by various environmental factors. Especially potatoes of long tubers are prone to these “sugar end” defects, such as, for example, the sorts “Russet Burbank” and “Shepody” that are frequently used for the production of French fries. This growth defect is of great economic importance, as the locally accumulated reducing sugars generate brown to black pigments in the course of heating, thus making the final potato product optically non-appealing and, hence, non-marketable. An essential problem of the “sugar end” defects is that they are not optically recognizable at the raw potatoes or potato parts, respectively, but will rather appear following heating in the kitchen or in the food processing industry, respectively, and will then result in frequent complaints. An additional aspect of at least one embodiment of the invention is the prevention of increased acryl amide formation when the potatoes are baked or fried. In particular French fries have become ill-famed as they contain acryl amide, a substance that may cause cancer. Acryl amide is generated when potatoes are baked or fried at high temperatures, by the starch contained in the potatoes being overheated. The most important starting material for acryl amide in foodstuff is the amino acid asparagine, predominantly present in potatoes and corn. The formation of acryl amide is further promoted by sugars such as glucose, this is substances which are also present in larger quantities in potatoes having “sugar end” defects.
Former approaches to the early recognition of “sugar end” defects on potatoes are based on heating test samples of potatoes upon harvest or at incoming goods inspections, followed by visual inspection by the operator personnel. If individual test samples show “sugar end” defects, rather frequently the entire charge of the potatoes is discarded, amounting for huge material losses and large losses for the producing company. Alternatively, all ends of the potatoes of the entire charge are cut off, if “sugar end” defects are present on the test sample. In this way, the material loss is decreased, due to the additional working process step of cutting off, however, the costs of labour and machines are increased. Furthermore, heating and inspecting test samples constitutes a time-consuming task, hindering a rapid processing of the potatoes.
Hence, it would be desirable to provide a method and a sensor unit for detecting “sugar end” defects in potatoes, which are not simply applied to test samples but rather enable a reliable examination of all potatoes, and this, moreover, inline in a single potato processing line. It would be further desirable to provide a machine for treating potatoes having “sugar end” defects, in which initially potatoes having “sugar end” defects are reliably detected and subsequently the potatoes having “sugar end” defects are either sorted out or treated by cutting off the parts in question.